Field
Embodiments described herein relate generally to a semiconductor memory device and a controlling method thereof.
Description of the Related Art
As one of semiconductor memory devices, there has been provided a flash memory. In particular, since its inexpensiveness and large capacitance, a NAND flash memory has been generally widely used. Up to the present, many techniques to further increase the capacitance of this NAND flash memory have been proposed. One of the techniques is a structure of three-dimensionally disposed memory cells. In such three-dimensional semiconductor memory device, the memory cells are disposed in a laminating direction. Conductive layers extend from the respective memory cells, which are disposed in the laminating direction. The memory cells each include memory films, which include electric charge accumulating layers, between a semiconductor layer, which will become a channel, and word lines. Such three-dimensional semiconductor memory device has been requested to speed up a writing operation and reduce power consumption.